This invention relates to gradient amplifiers and will have specific reference to a switch device for reconfiguring a plurality of stacked gradient amplifiers for use with a nuclear magnetic resonance imaging machine.
Nuclear magnetic resonance imaging (MRI) has revolutionized the medical field in the diagnosis and treatment of patients and has gained wide acceptance since its inception in the early 1970's. As is commonly known, MRI machines use large coils to set up a magnetic field into which the patient is inserted. To generate these large magnetic fields a plurality of power amplifiers associated with each of the coils is required. Typically two or three power amplifiers are associated with each of the three MRI coils or axes.
One of the most significant advances in MRI is the development of fast-scan technology. Fast-scan technology is used to view movable parts of the body, such as the patient's heart or joints. One drawback to using fast scan technology is that the voltage waveforms needed on the fast scan axis have unusually fast rise and fall times which require increased voltage to the coil. Therefore, the hospital or laboratories using fast scan technology have previously had the option of either buying additional amplifiers to be placed on all three axes or to use manual means to configure the system such that enough amplifiers (sufficient voltage) could be placed on the fast scan axis. A problem associated with the option of providing a sufficient voltage on all axes is the cost of additional amplifiers to the hospital. Similarly, there is machine down time when one must manually reconfigure the gradient amplifier.
A further problem experienced in MRI machines in general is associated with common fatigue and breakdown of the amplifiers. A malfunctioning amplifier causes the MRI machine to become inoperative. While it is possible for the hospital to maintain a standby amplifier at considerable cost, the replacement time for a technician to be called to the site and replace the down amplifier will be an additional expense for the hospital.